This invention relates to document feeding equipment for stripping and feeding documents one at a time from a stack of documents.
Although not limited in its application thereto, the document feeding equipment of the present invention is especially adapted for use in the rapid feeding of documents to a read station for reading by character recognition equipment and for further processing.
Various types of document feeders for feeding documents from the bottom or end of a stack are known in the art. With known prior devices, difficulties are encountered in the feed of documents of a relatively wide range of thicknesses over prolonged periods of time. Many such prior art devices are well adapted for reliably feeding one type of document such as a punched card or other document of constant thickness but are not well suited for the feeding of very thin documents, or documents whose thicknesses vary to an appreciable degree or documents which tend to cling together when they are fed. Moreover, many of the prior devices known to us which may accept documents of a range of thicknesses have no effective means for compensating for wear induced changes in dimensions and require relatively frequent adjustment or replacement of cricital parts such as feed rolls and the like.
As indicated above, the present invention is intended for use for feeding documents to a reader in optical character recognition equipment. It is desirable that such a device be capable on the one hand of feeding tissue paper thin documents such as airline or train tickets having a thickness of about 0.002 inches, and on the other hand being able to accommodate relatively thick card stock of the kind used for punched cards. It is desired that such documents be fed relatively rapidly and to the maximum extent possible, without operator intervention. It is also extremely desirable that the mechanism be capable of feeding documents over prolonged periods of time without the need for special servicing by skilled service personnel.
Particularly troublesome problems with apparatus of the kind described obviously arises when two documents are fed at the same time. Double feeding of documents means that information contained on one of the documents is not read by the optical character recognition equipment and if this happens with any frequency, reliability of the entire system is destroyed for data processing purposes. Detection of errors caused by double feeding is very difficult to detect and even when detected it is time consuming and costly since it usually requires some manual intervention on the part of the operator.
Examples of prior art feeders are shown in Rouan et al U.S. Pat. No. 2,273,287, Oaten U.S. Pat. No. 3,525,518 and Kolibas U.S. Pat. No. 3,838,851.